During the manufacture of one-layer corrugated paper material with outer layers, the corrugated paper strip is deformed wavelike between corrugated rollers, whereafter a starch adhesive is applied onto the two flat outer layers. This layer unit runs then through a drying zone, during which under the action of heat energy the water content is removed from the applied adhesive. For the manufacture of a two or three-layer strip, the described process stations are followed by the same process stations or a multiple of such process stations cumulatively placed in the production line. As a result, only after a complete finishing and drying of the one-layer strip has occurred can the second layer be manufactured, with which the intermediate layer is placed and glued together and exposed to a drying operation, etc. This process thus requires, for the multilayer corrugated paper strips, the correspondingly multiple length of the production line for a one-layer corrugated paper strip. Several hundred meters for a production line for multilayer corrugated paper material are hereby required. One must add, that due to the thickness of the layer material, which thickness increases because of the successively occurring stacking of the individual corrugated paper strips, the removal of water from the adhesive takes much longer during the drying operation because a portion of the applied heat energy is absorbed from the outer layers. An increase of the temperature in the drying stretch is not possible due to the temperature-sensitive paper material.
The aforementioned difficulties occur in particular if a corrugated paper material is to be manufactured which, as in the known case, is comprised of four or five single corrugated paper strips or of two prefabricated two-layer corrugated paper strips. For the manufacture of such a material in the usual manner of production, an extremely long production line which would far exceed the dimensions of a common production place and a very long process duration would be necessary, whereby one would have to add that due to the necessarily long-time and intensive heat treatment the paper material, if it does not burn, would certainly suffer damage due to the intensive heat treatment with respect to its self-elasticity and mechanical stability.
The basic purpose of the present invention is now to develop an apparatus for the manufacture of multilayer corrugated paper material in such a manner that, independent from the number and structure of the layers (corrugated paper strips) which must be connected, a short process duration and economical process sequence can be achieved compared with conventional methods, and that it is assured that a damaging effect of the process on the quality of the product can certainly be excluded.
This purpose is attained according to the present invention, by providing one of the corrugated paper strips, outer layers and/or intermediate layers, which are to be glued together, with a cold setting, preferably waterproof adhesive, and after placing the corrugated paper strips and/or intermediate or outer layers one on top of the other by running the thus obtained sheet unit through a compression station, in which the layers are pressed against one another with a mechanical pressure which only elastically deforms the corrugations of the corrugated paper strips.
Due to the fact that for connecting the individual corrugated paper strips a cold setting adhesive, a plastic adhesive, a dispersion adhesive or the like is used, all thermal effects do not exist during the connecting process which could, as above discussed, have disadvantageous effects on the paper material. In particular, the connection which takes place between the adhesive and the limit surfaces of the superposed materials is hereby independent from the thickness or from the number of the individual layers of the corrugated paper material. This independency permits, contrary to conventional methods of manufacture, to place two relatively thick, prefabricated corrugated paper strips on top of one another after the application of the adhesive and to connect same with one another by mechanical pressure without having to be concerned that the setting process does not take place at all or takes place only insufficiently, may be because of an insufficient penetration of the poorly heat-conducting material by the heat energy applied from outside. In a special manner, the process of the invention makes it possible that the process sequence is shorter in time and can be carried out by a shorter production line in which for each application of one individual layer a separate drying stretch is required. Due to the independence from thermal influences, the inventive process is particularly suited for very thick corrugated paper materials, as they are used for packing containers for heavy goods or also for living space walls or decorative walls. During the manufacture of such materials it is advantageous, that in the compression station the adhesive wetness can spread unhindered from the inside of the material to the outside, for example by heat energy flowing in from outside, where such adhesive wetness during the compression operation slightly wets the material layers and thus to a certain degree overcomes the mechanical tensions possibly existing in the corrugated paper strips and permits a planar, extensively tensionfree abutment of the limit surfaces of these corrugated paper strips on one another to form an extremely tight, gapless connection. By using waterproof adhesives, a closed waterproof layer is created in the material center, which layer, also in the case of injury to the material outer or inner side, prevents a moving of the wetness to the material layer lying on the other side of the waterproof layer.
According to a further development of the invention, at least two conventionally individually prefabricated two or multilayer corrugated paper strips are placed one on top of the other after applying the adhesive on only one of the directly adjacent outer layers of the corrugated paper strips and are fed together to the compression station. Corrugated paper strips can hereby be used which have two equally thick outer covers and one thinner intermediate cover. A particularly strong center material having a duplicate cover thickness is thereby obtained. By applying the adhesive onto the outer layer of only one of the strips, the process of manufacture is simplified in as far as during the time in which the adhesive is applied on the one strip, the other strip is fed to a superposing station, is turned possibly at 180.degree. and then united with the strip which has the adhesive thereon and which comes on a conveyor belt. These parallel running process steps can be adjusted to one another in such a manner that a continuous manufacturing sequence takes place.
According to a further development of the inventive process, two two or multilayer corrugated paper strips, each of which has on the one side a thin outer layer and on the other side a thick outer layer and after applying the adhesive onto the thin outer layer of one of these corrugated paper strips, are placed one on top of the other with their thin outer layers in engagement and are fed to the compression station. The two thin outer layers become united in a thick strong intermediate layer reinforced by the adhesive layer. A process for the manufacture of such a corrugated paper material can be constructed by providing one of the corrugated paper strips, which comes from an upstream production line which serves the manufacture of the two or multilayer corrugated paper strips or from a storage area, with an adhesive in an adhesive application station, while the second corrugated paper strip arriving from the upstream production line or from the storage area is fed to a superposing station, is turned 180.degree. and is placed onto the first corrugated paper strip which has been transported into the superposing station. A combination of the connecting line which glues together the multilayer strips with a production line of conventional type in which the individual strips are produced, is advantageous because in the production line the two-layer strips, for example, can be manufactured at relatively high running speed, while, as already discussed, in the following connecting line itself extremely thick strips can be united in one single, relatively short process step at a running speed of approximately 20 to 25 m. per minute. The running speed can also be increased to higher speeds, for example 70 m. per minute.
The corrugated paper strips which are to be glued together are hereby advantageously manufactured together in one single production line which is located upstream of the adhesive application station, are portioned and fed separately to the adhesive application station and to the superposing station.
According to a further development of the inventive process, all corrugated paper strips are manufactured together in one single production line and are thereafter fed in portioned sections to at least two parallel connecting lines which have each one adhesive application station, one superposing station and one compression station. This meets the situation that the running speed in the production line is possibly slightly faster than the one in the connecting line. Through this distribution of the portioned corrugated paper strips onto parallel connecting lines, the manufacture flow determined by the higher speed of the production line is not interrupted.
An apparatus for carrying out the above-discussed process is characterized by a connecting line which exists for the reciprocal connection of the corrugated paper strips, comprising an adhesive application station, in which at least one of the corrugated paper strips is provided with a continuous adhesive layer, a superposing station in which the corrugated paper strips which are to be connected are placed one on top of the other and of a compression station, in which the united corrugated paper strips are pressed against one another under mechanical pressure.
The compression station preferably has motor-driven roller pairs which are arranged one behind the other, whereby the distance between the rollers of one roller pair can preferably be adjusted individually. It has been proven to be advantageous in practice, if the rollers are slightly bellied. The contact pressure of these rollers can be adjusted exactly in consideration of the thickness of the material which is to be worked. In order to apply during the entire compression station an uninterrupted pressure onto the sheet unit, in a further development of the invention, the roller pairs are positioned with their axes of rotation skewed to the axis of transport direction for the corrugated paper strips.
According to a further development of the invention, the adhesive application station has a motor-driven roller pair, of which one of the rollers is connected with a container which contains a liquid adhesive. The liquid adhesive flows and spreads equally to all sides on the surface of the respective corrugated paper strip and assures a homogeneous, uninterrupted film of adhesive, which is also capable of evening out possibly existing unevennesses in the outer layer of the strip.
According to a still further development of the invention, a conveyor device is provided for the corrugated paper strips which are to be placed onto the corrugated paper strips which are provided with an adhesive, which conveyor device is connected on one side of the upstream production line before the adhesive application station and on the other side to the superposing station. This conveyor device takes the strips from the upstream production line outlet or from a storage area, for example in a two step succession, and feeds same to the superposing station bypassing the adhesive application station, at which superposing station the unification takes place.
An advantageous embodiment of the apparatus for carrying out the process exists in an upstream production line being connected before the connecting line, in which upstream production line the corrugated paper strips are manufactured which are subsequently connected, and a processing line being connected after the connecting line, in which processing line the connected corrugated paper strips are provided with bending folds or bending grooves and/or are portioned or cut. An outstanding advantage of the invention compared with conventional production lines is that it is possible without an excessive extension of the production line for corrugated paper material, which extension would be problematic in economical and technical respects, to combine a conventional production line, a connecting line and a finish processing line. It is possible to insert in the processing line various fixtures to manufacture bending folds, bending grooves or the like. Thus it is possible to provide in an advantageous manner in this processing line a milling device having a preferably V-shaped profile miller, with which profile miller bending or folding grooves can be produced in the finish glued corrugated paper strips. The provision of milling grooves has proven to be advantageous and necessary in particular in the case of the corrugated paper material which is often extremely thick and produced with the inventive process, because only such grooves permit a convenient, manual bending of particularly sharp folding edges in a packing. The profile millers can be precisely adjusted so that the milling groove does not hurt the waterproof adhesive film inside of the material.